1. Field of the Invention
The present invention relates to a sheet material fixing device which fixes a sheet material onto the peripheral surface of a rotating member.
2. Description of the Related Art
Printing plate exposure devices have been developed which record (expose) an image directly by a laser beam or the like onto an image forming layer (e.g., a photosensitive layer or a heat-sensitive layer) of a sheet-shaped printing plate (e.g., photopoly plate or a thermal plate).
The printing plate exposure device is equipped with, for example, a rotating drum. The rotating drum is hollow cylindrical, and both ends thereof are closed. A printing plate is conveyed on the peripheral surface of the rotating drum. A pressure-reducing blower communicates with the interior of the rotating drum. A large number of suction holes and suction grooves are formed in the peripheral surface of the rotating drum. When a printing plate is being conveyed on the peripheral surface of the rotating drum, the pressure at the interior of the rotating drum is reduced by the pressure-reducing blower. The printing plate is thereby vacuum-adsorbed via the many suction holes and suction grooves, and is fixed to the peripheral surface of the rotating drum.
A recording head portion is provided in a vicinity of the rotating drum. While the rotating drum is rotated at high speed, a light beam from the recording head portion is irradiated onto the printing plate which is fixed on the peripheral surface of the rotating drum. The printing plate is thereby subjected to exposure processing.
However, in this printing plate exposure device, the machining for forming the large number of suction holes and suction grooves in the peripheral surface of the rotating drum is costly, and in addition, the pressure-reducing blower is required. Accordingly, problems arise in that the manufacturing costs increase, and that, due to the pressure-reducing blower, the surface area required for placement increases and noise is generated.
Yet another problem arises in addition to the aforementioned problems. In printing plate exposure devices which are currently being developed, the printing plate is fixed to the peripheral surface of the rotating drum by the leading end and the trailing end of the printing plate, which is being conveyed on the peripheral surface of the rotating drum, being pressed against the peripheral surface by leading end clamps and trailing end clamps, respectively.
However, in such a printing plate exposure device, the printing plate is not adsorbed to the peripheral surface of the rotating drum. Accordingly, at the time when the rotating drum is rotated at high speed, if the printing plate pressing portions of the leading end clamps and the trailing end clamps deform due to centrifugal force, it is difficult to uniformly press the leading end and the trailing end of the printing plate against the peripheral surface of the rotating drum. Thus, it is difficult to make the entire printing plate fit tightly to the peripheral surface of the rotating drum.